


lux ex tenebris

by daemon



Category: B: The Beginning (Anime)
Genre: Aftermath, Age Difference, Alternate Universe - Canon Divergence, Developing Relationship, Domestic Fluff, M/M, Mild Sexual Content, Recovery, Slice of Life, Stolen Moments
Language: English
Status: Completed
Published: 2018-08-21
Updated: 2018-10-03
Packaged: 2019-06-30 10:54:14
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 7
Words: 3,859
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15750237
Author URL: https://archiveofourown.org/users/daemon/pseuds/daemon
Summary: Keith learns to share space and Koku learns to fill it.(Bit and pieces, here and there.)





	1. light

**Author's Note:**

  * For [skinandbones](https://archiveofourown.org/users/skinandbones/gifts).
  * Inspired by [Inside Ourselves](https://archiveofourown.org/works/15688968) by [skinandbones](https://archiveofourown.org/users/skinandbones/pseuds/skinandbones). 



> i felt particularly inspired and i definitely want to write more of this pair.
> 
> ( ~~i love pairs with age differences okay, don't look at me.~~ )

Keith Flick didn't think often of the events that led him to this moment, nor did he care enough to dwell on them. All he thought of now were the deep, blue-black feathers as he buried his hands in them, combing his fingers between each feather just to fix them and smooth them out. A quiet groan left the younger man as he made his way up to the joints, gently poking and prodding at the muscle tissue and prickled flesh beneath the downy layer to help relax the wing.

"Must've hurt when you fell."

There's a sigh that catches his attention, and when he glances at the other, dark teal is watching him through a curtain of ebony. A smile tugs at soft lips and Keith finds himself drawn to closer to _his_ gravity.

"From heaven? Are you calling me Satan?"

The smile only encourages him.

-

"What's going on here?"

It's one of those truly surreal moments and he seems to have a lot of those lately (it's been a year and he still can't believe this is his reality). Keith has given up trying to keep _him_ out, even deigned to give up a copy of his house key, shared meals with him, relinquished old shirts and shorts (marveling how they hang off narrow shoulders or shred with unfurled wings), and sometimes his bed.

But oddly enough, out of everything that happened from a year ago to now— it's seeing Koku in one of his hoodies with his long black hair pulled back in a bun; it's the rectangular black-rimmed glasses perched on his nose and magnifying his heterochromatic eyes; it's his lithe form curled up with his bare legs pulled to his chest, body comfortably nestled in a giant beanbag.

Koku peeks over the rim, eyes dragging reluctantly from the book in his hands and purposely ignoring the way Keith's gaze surveys the piles of library books surrounding the younger man. Keith watches him, a sigh threatening to escape his throat as Koku cradles the book to his chest and grins at him.

"Just reading."

The sigh leaves him nonetheless and Koku grins wider.

-

Koku knows that Keith is very good at faking sleep. Koku also knows that Keith is very good at pretending to be asleep for as long as he wants to. He's been laying here atop the covers for thirty minutes, waiting for the older man to wake, or rather, _wake up._

"Keith." Nothing.

Koku narrowed his eyes, " _Keith_."

Still nothing.

Puffing his cheeks in a gesture far too similar to Lily at full petulance, Koku huffed in annoyance and crawled under the covers to burrow up against Keith. A sleepy grunt sounded from the elder as Koku snaked an arm around his waist, resting his head on the pillow next to Keith's. For a long while, between the slow perusal of his lined features and the silent count of his breaths.

It wasn't until Koku brought a hand up and traced feather-light fingertips through Keith's stubble, did the detective finally open one hazy eye to stare at him. Koku watched him, meeting that gaze easily enough, and continued his slow exploration along Keith's jawline to the back of his neck. He stopped there, patient and waiting as Keith opened both eyes to meet his.

Koku whispers, _"Kiss me,"_ in the space between them and Keith blinks, more awake now.

The gentle squeeze on the back of his neck is unnecessary, not when he's already moving and pinning Koku to the sheets, and claiming that smiling mouth for his own.

-


	2. holy

Keith can sleep anywhere.

It was a fact, indisputable and clad in iron; you could find the man precariously perched on the edge of a cliff and he'd be snoring despite the wild winds rushing up to meet him. So it wasn't a surprise really, when Lily burst into Keith's apartment— with Yuna trailing after and her arms full of shopping bags— to find him facedown on the floor, his head in Koku's lap, and Koku using his skull as a prop for his latest book.

Both women froze in the entry, staring at the—admittedly— _normal_ scene before them. A soft snort and frustrated grumbling sounded from Keith as he continued to sleep through the ruckus and noise of Lily and Yuna setting their bags and things down on the dining table, Yuna barely hiding an amused smile as Koku threaded his fingers through Keith's wild hair in order to soothe the detective back to sleep again.

Lily smirked, clapping her hands together with an over-exaggerated cooing noise that earned her an odd look from Koku, "Now isn't that the sweetest."

Without fail, Keith raised a hand and promptly flipped her off.

-

It's happened before, when it surprised them both; an unexpected result to a fumbled first attempt at sex. He remembered the way Koku's back had arched and his eyes squeezed shut as the cries escaped his bitten lips, and the sudden violence of his wings bursting from his back when his orgasm ripped through him. It had been a beautiful sight, forever engraved into Keith's memory banks, and he'd nearly blacked out after.

It was possibly the closest he'd been to god—the fact he was _buried_ in one, well he'd think on that another day. When he could breathe properly, of course.

Now here he was again, with his hands gripping a narrow waist and nails digging into sweat-slicked skin, attempting to redirect the stuttering rhythm of the body moving on top of his. But Koku was _something else_ in these moments, the full breadth of his inhuman nature on display in these moments of rapture and Keith was absolutely _ruined_ by it.

Koku's hair was a mess, sticking out in wild directions and tangled from his brief time pinned to the pillows; Keith liked the way his choppy bangs stuck to his forehead, how his hair fell over his shoulders or fanned out when he tossed his head back. He liked the flush in his cheeks as it spread to his neck and chest, his lips reddened and wet from heavy kisses, and the pink lines trailing down his sides from Keith's own lust-fueled desperation.

" _Kei—th, fuck—_ " Koku's voice bounced off the walls, a chant of Keith's name spilling rough and breathless from his lips as he moved, lifting and dropping himself quicker, losing his rhythm the harder he grinds down until _finally_ —

Keith inhaled sharply when he felt the sudden jerk of Koku's body above him, fixated his eyes on the glorious vision of Koku arching— only for the younger man to pitch forward and kiss him in the same brutal moment his wings tore from his back and a crash sounded from the bedside. His black wings trembled and twitched above them, spreading out and flapping erratically and uncoordinated, nearly reflecting the same wild sensations tearing through Koku's body as he slowed to a stop at last and collapsed on Keith. He kept trying to kiss him, trailing kisses from his mouth to Keith's neck and chest where he finally lay his head. His wings drooped, and fanned out on either side of the bed like boneless appendages as Koku basked in the aftermath, where Keith was combing shaking fingers through his damp hair in a rare show of affection.

Deep teal and cobalt eyes blinked open and Keith felt more than just pleasure tingling beneath his skin to see the matching smile, too focused he was on that to care about the extra weight of the wings or the sticky mess between their bodies.

He knew when he could finally function again, he'd find scattered feathers everywhere, he'd find the source of the crash next to their bedside, and he'd be collecting the remains for days. He knew he'd be mildly irritated, and a little exasperated, but the moments like this made it worth the effort.

After a while, when the sweat of their skin has cooled and he felt a shiver run through Koku, he finally extricated himself from the younger and carefully nudged a wing out of the way to head for the shower.

He remembered to check the floor first, before setting his feet down; taking note of the only casualty this round that was his bedside lamp. A pitiful loss compared to the vase during last time. From behind him, a slender arm appeared and wrapped around his waist, joined by its mate as Keith stood from the bed and walked towards the bathroom, dragging the limp weight behind him. Koku held tight like a stubborn barnacle, both wings and legs trailing behind the detective in his slow trek across the room; truthfully, it was ridiculous, secretly, it was... kind of endearing, but Keith would never admit to it.

Keith went through the motions, bath filling, water hot, towels laid out— all with his whining barnacle still attached.

"Off. Bath. Now," is all he had to say in order for Koku to slump bonelessly on the rug, looking up at Keith with a half-drunk expression.

Holding out his hands, he smiled to himself as Koku's wings dissipated in a fall of iridescent black, each feather catching the light like prisms until they faded. Helping his boneless lover in the tub and stepping in behind him, Keith pulled the younger against his chest and settled in.

"Feel better?" Keith mumbled, nuzzling into the hair behind his ear to press a light kiss there.

"Much better." Koku shifted, wiggling a bit to get comfortable in the space between Keith's long legs, and rubbed his hands lazily up and down the man's thighs; he could hear the content smile in that sleepy tone, and felt something equally content and hopeful settle in his ribs.

Beneath their flesh, their bones were different, a contrast of night and day, god and man. But at the end of day, this is all that mattered.

-

"—and you needed a new lamp anyway, that one was hideous."

"It was a gift from my mother."

"Well... she has bad taste."

"Respect your elders."

" _Make me_." 


	3. routine

It becomes an unintentional routine.

Koku woke first usually, slipping from the covers to wash up and start breakfast. Simple things, like eggs and rice, bacon or toast, maybe a bit of fish if Keith had bothered to pick some up. There was coffee, the strong scent of it meant to lure the other man from the bedroom after early attempts to rouse him failed.

Koku grabbed the kettle as it began whistling, and just as he lifted it off the burner, he heard the unmistakable sound of a body hitting the floor and groaning thereafter. Stumbling steps thumped through the apartment and Koku just barely set the kettle down again in time for a mess of hair to drop on his shoulder and lanky arms wrapped tightly around his waist.

From there on, the routine continued.

With Keith wrapped around him, Koku continued with breakfast, finished the coffee, and the smile on his face never disappeared as Keith moved with him. Their awkward shuffle around the kitchen in the early hours was perhaps a favorite piece of this fresh chance, from Keith's sleepy mumbles against his neck, to Yuna's cheerful smiles as she sets the table and starts plating their meal.

When they finally sit at the table, each taking their spots on the benches—with Lily joining them soon after to make sure Keith leaves on time— Koku still has Keith pressed against his side, an arm around his waist, chin on his shoulder, and sleepy eyes drooping between slow bites.

It's when he's finishing up his plate is usually when it happens, when Keith will finish first and hold him closer, and nuzzle into his neck amidst the chatter and caress kisses into his skin. They tickle because of Keith's beard, and taste bitter from his coffee when he makes his way to Koku's smiling lips.

But they're warm, and sweet, and just enough to hold him over until the next kiss.

-


	4. sweet

"You smell like my shampoo."

Koku didn't meet his gaze.

Not that he could, with Keith lingering over his shoulder; he was munching on a pastry, the powdered sugar coated his lips and Keith blinked once, twice, before curving a hand under Koku's jaw and guiding their lips together. The kiss tasted sweet, with cream and berry compote and flaky pastry. Behind them, he heard Yuna giggle, and say her goodbyes as she left for the day for her part-time job.

Truthfully, she knew it was dangerous leaving them alone, because now it was guaranteed they'd never get anything done today without supervision.

Koku made a noise in his throat, soft and content, only breaking from the kiss long enough to finish the last bites of his pastry. He stood there looking like he was trying not to smile, as Keith pulled him close and kissed him again, peppering little ones all over his face just to elicit a laugh from the younger man. They were alone now and usually that meant Keith felt no need to mute his affections.

Keith grumbled as he tucked his face against Koku's neck, sighing when Koku wrapped slender arms around his shoulders, "Why does my soap smell better on you?"

Koku shrugged, "Yuna confiscated mine because she liked it, didn't think you'd mind."

"I don't." He pressed another kiss to Koku's pulse point, feeling it jump the tighter he held the other, "Smells good on you."

Koku hummed, only for another laugh to escape him when Keith blew a raspberry against his neck like a _child_ , "Wha— _stop that_ —Keith!"

Keith kept it up until a pounding on the front door announced Lily's arrival, her boisterous voice yelling through the door about degenerate detectives innocent gods, and Keith merely yelled back that Koku is _nowhere_ _near innocent!_

Koku snorted as he shoved him off and towards the door, "Go. Be an adult. Bring home vegetables for dinner. Yuna's making stew."

Keith made a face as he opened the door, barely dodging just in time to avoid Lily's fist for another barrage on the door, "Yuna cooks?"

Koku shrugged, "Just stew, apparently." Then he waved at Lily with a smile, "Make sure he comes home on time, please?"

Lily grinned as she grabbed the detective by the arm, "Of course, _your majesty_."

The perfect blush that spread like wildfire across Koku's face is perhaps the one thing that kept Keith going throughout the day.

-


	5. king

**Notes for the Chapter:**

> i dunno man, i've had the same song on repeat for almost an hour writing this.

They come together slowly. A gradual build of tension that escalates as time goes on. When it becomes too much, the aftermath is undeniable; from the bruises left on each other to the kisses shared with so much heat they might explode. And they do explode, eventually. They're like two wild stars colliding and going supernova, each a black hole trying to swallow one another whole.

The taste of blood on his lips is sharp and nearly breaks the spell; he'd left the window open on purpose, and invitation for Koku to enter whenever he returned. He'd smelled the blood before he saw it, let it slip from his mind the moment those iridescent black wings spread out behind his as he landed on the sill. Koku's skin faded from deep indigo to a moonlit pale, the eye of the Jetblack King blinking from existence and returning to enchanting teal, dark blue blinking away the feral haze as Koku stumbled across the floor.

His clothes were torn and and splattered with dark spots, the back of his tee was shredded and came off easily as his wings molted apart in a trail across the floor as he approached Keith on the bed. Keith never once felt anything but awed by him, so terrible and beautiful, so wild and ethereal; even when the most logical parts of himself knew better, knew how dangerous the King was, and that he walked the lines of insanity every day simply by inviting this godling into his home— he was still _attached_.

"— _eith_ —" Koku's voice was rough, broken, a rasp as his tongue wrapped around his name, and coupled with the desperation in his eyes, and the hands reaching for Keith; he couldn't deny him anything even if the world stood in the way.

Keith sat up and grunted when Koku fell into him, felt hands grasping desperate and hungry in his hair, and lips crushing against his own until every neuron, cell, and fiber of his being was focused on _Koku_. There it is again, that _supernova_ in his mind bursting as this quiet, murderous gifts him this affection. He doesn't believe in god, he doesn't believe perfection; but he believes in humanity, hopes for the best despite the worst that he's seen, believes in this taste of heaven that he hopes will remain untainted.

But this is the Jetblack King, a creature of legend masquerading as human, trying so hard to _learn_ and _feel_ and _understand._ A myth attained by avarice is nothing to place his faith in, but he knows here and now it's a powerful thing to be considered _home_ by a _god_.

"Keith," Koku mumbled against his lips, nibbling and licking, claiming kiss after kiss despite the tang of iron seeping through the growing lust, "You're thinking too loudly…"

Keith broke away and swallowed, licking his lips and tasting _Koku_ and something _else_ , "Bath. Bath first." His own voice is just as wrecked already and his body is ignoring his brain, and Koku's eyes are so wide and frightening and _wanting_.

Koku smiled, tentative and relieved, "Okay."

Keith didn't believe in perfection, didn't care for infallible deities, but he believed in this.

_I believe in you and me_ , he thinks, herding Koku towards the bathroom.

-


	6. fluff

"What's in the box?"

Koku merely smiled at him instead and didn't answer as he disappeared into the other bedroom. Keith was suspicious. Of course he was. Koku had a tendency to bring home all sorts of strange things, with zero hindrance from Yuna. Ever since they’d cleaned up the spare room and set it up for the young woman, sharing the small apartment had become much more manageable.

That is, until Koku started bringing home mysterious boxes and hiding them in Yuna's room.

(It was no longer _that room_ , it was no longer _her_ room. It was no longer the place where Keith tried to keep Erika alive in endless strings of numbers, equations sprawling across the walls and marked in red on the ceiling.

Keith had—after the death of Gilbert and the closure of Erika's case at last—quietly began to clean the room of markers and chalk. He scrubbed the walls and ceiling, painted everything that remained, and enlisted Kaela's help in finding furniture to fit for Yuna.

Keith had learned to let go, and he knew it was in part thanks to Koku.)

Koku, who shut the door behind himself with a chuckle, shuffled around in the bedroom, andKeith narrowed his eyes when he heard a soft shushing noise coming from the room that piqued his curiosity and suspicious further.

" _Koku_."

The bedroom door creaked open and one teal eye blinked at him innocently in the crack, "Yes?"

_"What's in the damn box?"_

A smirk appeared next and the door clicked shut.

_"Koku!"_

A muffled _'Kiss my ass~!'_ drifted out in sing-song through the wood and Keith rolled his eyes. Koku has clearly spent too much time around Lily.

(Later, after returning from the library, he finds _kittens_ running around his apartment. Goddamn, fluffy fucking, mewling, stumbling, squeaky _kittens_. What the _fuck_ , Koku.)


	7. pathway

Koku didn't do depression, nor do sadness or grief. Koku was impossible fury strangled and buried beneath a facade of calm and sweetness. It was interesting to witness the rage just beyond his carefully constructed face, and rarely did he allow Keith or Yuna to witness it these days. His sadness was buried deeper, overwhelmed instead by the hated and grief that lined his black bones. Keith suspected it was genetic; the black does not forget and the bones cannot lie.

There would always be something inhuman and ethereal about Koku and Yuna both, something feral about Koku and disconnected in Yuna. As children, they had been allowed to be kids, innocent to the ancient power writ deep in their DNA; as adults, made cruel and remorseless by their circumstances, broken and scarcely hopeful for a meeting that might have never happened.

Keith sees it sometimes, watches it caress the surface and poke through the flesh like broken bones and torn sinew. Koku tried, he really did, to contain his bloodlust when it dared to surface. So Keith offers quiet compromise: find the Reggies on the edge, those that remain and can no longer hide their disposition, and claim them.

It was one of the few ways to appease the beast in his blood and keep him sane. It worried Keith, that his subtle disregard for the failed experimental godlings meant his priorities had changed. If Koku was able to maintain his sanity, fight his fate a while longer, and keep his instincts from overwhelming him— Keith believed this was worth it.

( _He had no choice. This is his life now. This is the path they had chosen. This is the door they opened together._ )

So when Koku would appear on his windowsill in the dead of night, the moon bright against his back where his wings had begun to fade in a burst of feathers, and dark, dark blood splattered against his ruined clothes—

Keith would be there, pulling him inside and shutting the windows, and herding across the room to the bathroom. As his skin faded from black to pale, as his eye returned from the Black King's to his natural teal, and Keith took notice of the adrenaline-driven trembling in his younger partner; Koku would cling to him, lean into his embrace and allow himself to be nudged and prodded into the hot shower until the two of them were both under the spray.

"Koku, head back," Keith whispered, lathering shampoo in his hands and feeling a half-smile tug at his lips when the other complied, " and eyes closed, please."

Koku shot him a look for a moment before tilting his head back and closing his eyes, allowing Keith to massage his fingers into his messy hair, scrubbing the blood and grime from the black strands until it rinsed clean. It's these unguarded moments that Keith has learned to appreciate; the relief once the storm has passed and the calm returning as the minutes pass.

He can feel it, as he works his fingertips through Koku's hair, combing it as the the suds rinse and the tension bleeds out of Koku's neck and shoulders; that fury is receding, returning to its slumber for now. Pleasant goosebumps take its place instead, a slow upward curve of his mouth, and a soft sigh.

Koku was coming back to himself and Keith didn't think he could do anything else but lead the way home.

(He even sealed that silent promise to himself with a kiss.)


End file.
